Sudden death is a major health care problem that affects thousands of lives
everyday worldwide. In the past decades, western epidemiological and scientific
data on sudden death had allowed better understanding of the underlying etiology
and enabled development of strategies in secondary prevention of out-of-hospital
sudden death. Despite their large population, Asian countries have relatively
little published data on sudden death.1,2

Incidence and Demographics of Sudden Death in Hong Kong

The first territory-wide survey on sudden death in the Hong Kong SAR was conducted
by the Cardiology Division, Department of Medicine, University of Hong Kong.
This survey shows an incidence of 1.8 sudden deaths per 100,000 population in
the year 1997. Out of 1204 cases of out-of-hospital sudden deaths reported to
the coroner, the underlying causes were acute myocardial infarction in 31%,
coronary artery disease in 26%, hypertensive heart diseases in 14%, ruptured
aortic aneurysm in 6%, cardiomyopathies in 5%, other cardiovascular diseases
in 7%, and non-cardiovascular causes in 11%. In less than 1% of these cases,
no structural abnormality could be identified by postmortem examination. (Dr
K Lee, unpublished data)

Implications

This incidence is much lower compared to figures of the western world. In the
United States, the annual incidence of sudden death is estimated to be 18 per
100,000 population.3 Even after this is adjusted
for a lower incidence of coronary artery disease in Hong Kong, the sudden death
rate is still significantly lower than the western figures. Apart from this,
the proportions of coronary artery disease and other underlying causes of sudden
deaths are quite similar, suggesting that the propensity to sudden death may
be genuinely low among the population in Hong Kong. Whether this is explained
by genetic, dietary or socio-economical factors remain to be resolved.

Post-infarct Ventricular Arrhythmia

Post-infarct ventricular arrhythmia and sudden death is common among western
population. However, an analysis of the long-term outcome of just over 300 patients
admitted into a regional hospital with acute myocardial infarction shows a 2-year
sudden death rate of only 1.7%.4 The ICD implantation
rate in Hong Kong is around 10 per million population per year, a figure much
lower than the average of 50-200 per million of the western societies. As the
health-care system in Hong Kong allows provision of full financial assistance
to patients who cannot afford the device, this low implant rate is not solely
due to economical reasons. In order to account for the reduced incidence of
sudden death among Hong Kong Chinese, we need to pursue further studies to elucidate
the mechanism of the apparent "protection" against malignant ventricular
arrhythmia in Chinese.

Idiopathic VF Syndromes

Since Brugada described the syndrome of sudden death in patients with apparently
normal heart and ST elevation over V1 to V3, it has come
to general consensus that symptomatic patients with this syndrome is predisposed
to malignant ventricular arrhythmia. However, both the incidence and natural
history of asymptomatic individuals having a similar ECG pattern are largely
unclear. Contrary to the belief that the "sudden unexplained death syndrome"
is prevalent in Asia,5 the incidence of sudden death
with no identifiable structural cause is less than 1% of all sudden deaths in
Hong Kong. These handful of cases may comprise other entities like Wolff-Parkinson-White
syndrome, congenital or acquired long QT syndrome, and unrevealed drug intoxication.6
This finding may help to call for more scientific data to halt the unwarranted
enthusiasm in diagnosing and treating "asymptomatic Brugada syndrome"
in individuals with suspicious ECG pattern.

Conclusion

This first territory-wide survey of sudden death in Hong Kong reveals inspiring
findings and substantiates previous observation about the low incidence of sudden
death among Chinese. It would be interesting and important to find out what
makes the difference.